Beginner Bluetooth Question - Bluetooth v4.0 and integrated microcontroller?

Look at the CC2540 and CC2541

Hi, Andrew

A couple of questions that may help with search: 

1. Does your device require dual-mode BT 4.0 (that is, both full-speed and LE connectivity)?

2. How much computation power and which peripherals do you need?

3. Are you concerned about power consumption? 

 AFAIK, TI has both BLE-specialized device (CC254x line, with 8051 MCU core) and dual-mode devices based on Stonesheet stack (which runs on certain devices from CC256x family, which uses CC430 MCU core). The former, being BLE devices, could be nicely optimized for low-power standby. Thus, there is no problem in general - you have MCU and RF core in one.

The slippery part is that many RF SoCs have their MCU core already burdened with system tasks, and have RF core as high-priority core user. This may somewhat limit programmer's ability to use MCU in old-fashioned way, full-power, and confine him (or her) to device API. That is not limited to TI products - I've had rather disastrous experience due to overall design mistake while trying to utilize BlueGiga's Casira without crippling essential radio functionality. There's nothing wrong with it (a price for having both fully functional RF endpoint and user program running on same device), but one should keep it in mind.

The good part, though, is that evaluation modules are not expensive these days, so building first prototype won't take ages.

Hi Oleg,

Firstly, thank you very much for your comprehensive reply, I really appreciate it.

The device would be paired to mobile phones and does not need a great range or data transmission rate. Is LE BT 4.0 backward compatible with full speed devices (older mobile phones for example) at the lower data rate? The features of full speed are not needed, but if it would make the device compatible with the Iphone 3G for example then I may consider it.

The BT would be in no means intensive usage  it is very much a secondary function - data would only be transmitted to the phone when the device was switched on and then when it was switched off. The data would only be perhaps 10KB in total in each transmission (which would typically be 10 to 30 minutes apart).

The computational power needed is not particularly great - I have an early prototype running on an Arduino (ATmega168) with a 16 Mhz clock and it seems ample.

The specification for chip I put together yesterday looked something like this and would be the ideal really:

Vdd = ~3.7V

Digital High/Low (1.2V min high, 0.6V max low) and PWM output functionality

Two way Bluetooth v4.0 communication

5-10m range

Data rate can be low (BLE ~200 kbit/s is ample)

Over the air chip reprogramming (to and from Iphone/Android app)

Built in radio

Built in crystal oscillator

Wake from standby on button press

Low standby power consumption

Random number generation (non essential)

Time tracking ability (millis() or similar)

Hey Andrew,

BT Low Energy (i.e. Bluetooth 4.0) is only compaitble with iPhone 4S and iPhone 5, iPad Retina.

What are you designing?

Ben

Hi Ben,

I can't go into too many details, but if you think along the lines of a small battery powered (90mah) activity monitor in the form of a wristband, like the Jawbone up or Fitbit.

Many thanks,

Andy

Sounds cool... are you in the UK?

I am indeed. Currently only a two man project, but from the prototypes so far it's looking promising. The next step will be to find an appropriate BT/MCU development kit / evaulation board and get that interfaced with a portable device and the current evaluation boards for the other parts of the circuit.

As I mentioned before, the BT is not required to send a large amount of data or data often to an app; only when the device is switched on or off or when the mode of the device is changed.

Cool.  I'm in the Midlands.

We're doing stuff with BT LE / iPhones etc... we have a prototype working with the CC2540 / iPhone and it's pretty good.  Once the BLEStack 1.3 is released (imminent) and iOS 6.1, it'll be pretty solid and tested.

If you need any help, give me a shout.

Cheers

Thanks Ben. I'm based in Gloucestershire.

I don't supposed you've researched certification costs for European and US markets? I've seen some estimates of $100k for worldwide which would seem to make usage of a CC2540 that wasn't already embedded into a certified module cost prohibitive unless it was in very large quantities?

Andy

I used to work in Swindon and Cheltenham! I preferered one to the other, I'm sure you can guess which lol

re. certification, Sadly I don't, I've heard similar rumours though.

Ben

Hi, Andrew

Dual-mode BT 4.0 devices may be backward-compatible, but single-mode BLE-only devices are not. If compatibility with BT Classic is essential, then CC254x family won't suit you, look at CC256x devices.

Also, reaching 200 kbit/s number may be hard, if not impossible, on BLE. But you'll probably be well-off with much lower speed and longer transfer, if they (transfers that is) happen rarely.

Regarding MCU power: if it fits AT168 at 16 MHz, it is not hefty. On the other hand, it is probably bare chip without high-priority RF routines running. I guess it is somewhat trial-and-error then.

Unfortunately, I have no knowledge of implemeting reliable ISP over radio for TI chips.

BR,

Oleg. 

Hi Oleg,

Thank you once again for such an informative answer. It seems the CC254x would be suitable for my needs.

Have you had any previous experience with certification and what kind of cost has it incurred if you don't mind my asking?

Kind regards,

Andy

Hi, Andrew

No, unfortunately we've never tried to certify BLE-powered equipment, simply because we've turned to using wireless links only recently.

Regarding compatibility, newer Apple products (from iPhone 4 and upwards) should support LE Bluetooth, as well as few other devices like Nexus 7 and GN10 (or at least Wiki says so). If you're not terribly concerned about compatibility with other devices, CC254x is good to go.

BR,

Oleg 

Hi Andy

If the massive initial capital requirement is an issue, you can always go for an already certified module. There are many out there, but BR-LE4.0-S2 is an example from Blue Radios. Its Basically a CC2540 with antenna and can around it, and is already certified. Might even be useful in getting your product to market sooner until you can sort out certification of your own module. They are substantially more expensive though.

Regards

Tielman

We found certification relatively easy with CC2540 - passed FCC first time with no RF optimisation. 

hey Eng, any ballpark on cost for the certification?

I believe one of the TI guys said there was going to be a document coming about how to get certified.  Haven't found it yet though

I was under the impression that the Bluetooth device has to be certified by both the regional body FCC / CE and then also by the BT Special Interest Group?

I am under the same impression.

What kind of volumes are you looking at for first production run?

There is a wiki page about Bluetooth low energy and radio certification on the wiki page:

http://processors.wiki.ti.com/index.php/How_to_Certify_your_Bluetooth_product

2-3K $US

Jonathan Cohn said:

hey Eng, any ballpark on cost for the certification?

I believe one of the TI guys said there was going to be a document coming about how to get certified.  Haven't found it yet though

oh, not as bad as I was expecting.  I was expecting $20k+

I guess since the chip itself is already certified, only the peripheral as a whole needs to be qualified, which costs less.

Hi Ben,

Quick question, I am interested in  the CC2540. I am planning on using it for a transmitter that will alert the iphone via bluetooth that the transmitter has moved so far away from the iphone. Is the CC22540 the appropiate chip that will work for my idea?

thanks

chris